An electronic device is susceptible to external electromagnetic interference. Electromagnetic shielding limits electromagnetic fields from reaching the electronic device, or specific electronic components within the electronic device, and is typically accomplished using a barrier made of conductive material. Electromagnetic shielding used to block radio frequency electromagnetic radiation is also known as RF shielding. Common materials used for electromagnetic shielding include sheet metal, metal mesh, and metal foam. The barrier is either an unbroken conductive surface or approximates an unbroken conductive surface. Holes in the conductive material must be smaller than the wavelength of the electromagnetic radiation that is being kept out, or the barrier will not effectively approximate an unbroken conducting surface. Another commonly used shielding method, especially with electronic goods housed in plastic enclosures, is to coat the inside of the enclosure with a metallic ink or similar material. The metallic ink includes a carrier material loaded with a suitable metal, such as copper or nickel, in the form of very small particulates. The metallic ink is sprayed on to the enclosure and, once dry, produces a continuous conductive layer of metal, which is then electrically coupled to a chassis ground of the equipment, thereby providing effective shielding.
In some applications, RF shielding is currently provided using a metal can shield over a high density substrate that is populated with electronic components. An RF shield is provided once the metal can is connected and conductively coupled to a ground plane included on the substrate. The metal can is connected to the ground plane via a guard ring on the substrate. The guard ring is positioned on a top surface of the substrate and coupled to the ground plane. The metal can is connected to the guard ring either mechanically or using solder. The metal can provides a radio frequency shielding capability, but increases the height of the component and typically increases the cost. With electronics moving toward miniaturization, increased size is not desirable. Also, metal cans become a dedicated piece part for a particular form factor module. The particular form factor must be accounted for in the manufacturing process. In applications that require environmental protection of the electronic components, such as protection against corrosion, humidity, and mechanical stress, the metal can is under-filled to cover the electronic components. The under-fill material is relatively expensive and the process of adding the under-fill requires additional steps in the manufacturing process.